We have 14 panels, installed in 2016. Apart from the first few hot months we have paid nothing for electric. The credit that we build up over the non A/C months pays for the hot months. We got city and federal rebates/tax credits, but it still cost a goodly chunk of money; supposedly it will pay for itself in 10 or so years and the system is good for 20+ years. We thought it a fitting memorial to my mother, and used the small inheritance from her to pay for it.